On 06/11/2020 20:59, F wrote:
We've got a patio made up of light coloured concrete paving slabs with a
slightly rough texture. I've used a Karcher power washer to remove the
compost that the resident gardener has managed to tread into them but
there's a green stain (algae?) that's pretty resistant to removal.

Anyone got any suggestions on what might shift it?



I use diluted bleach in a large watering can to clean my patio, and have
done so for years. It's as clean now as it was just after it was first laid.